Part III: Conservation and Management438
Knowledge concerning AMR bacteria circulating in wildlife
is currently limited, although available literature suggests that
this wild compartment could provide important insights into the
AMR emergence and persistence (Allen et al. 2010; Wellington
et al. 2013). Theoretically, wild animals are not treated with
antibiotics, but their association, both direct and indirect, with
humans, livestock, domestic animals or humanized environ-
ments can enhance their contact with selective agents, com-
mensals from humans and other species, as well as with resistant
bacteria. This contact is considered to promote adaptation
mechanisms of commensal bacteria and horizontal transfer of
resistance genes to the bacterial community of wildlife.
It is generally accepted that wildlife populations living in
close proximity to humans or agricultural areas exhibit higher
levels of resistance than those living in more remote, natural
areas (Kozak et al. 2009; Allen et al. 2011). Ninety-five percent
of the bacterial isolates from mice and voles captured in rural
England were resistant to antibiotics (Gilliver et al. 1999), even
though these authors argued that these rodents were supposed
to have had no contact with antibiotics. On the contrary, natu-
ral populations of moose, deer, and voles in Finland had almost
no resistance, leading the authors to suggest that the overall
weight of antibiotic use and agricultural activity was higher in
England than in Finland (Österblad et al. 2001). These find-
ings suggest that human activities influence antibiotic resist-
ance in wildlife. Similar associations were found in other
studies – mountain gorillas (Gorilla gorilla beringei) in contact
with humans harbour more antibiotic-resistant enteric bacteria
than those in remote areas (Rwego et al. 2008); and enteric bacte-
ria from land iguanas (Conolophus pallidus) in the remote Santa
Fe (Galápagos Archipelago) showed substantial lack of acquired
antibiotic resistance (Thaller et al. 2010). Interestingly, resist-
ant bacteria have also been described in remote, low anthropo-
genic-impacted areas, such as the Arctic. Sjölund et al. (2008)
recovered Escherichia coli-resistant isolates from Arctic birds.
Among several reasons, these authors suggested that bacteria
from migratory birds can acquire antibiotic resistance during
bird migratory stop-overs, which therefore can act as reservoirs
and long-distance dispersers of antibiotic-resistant bacteria.
This is clear evidence of the potential contribution of a macro-
ecology framework to disentangle the complexity of AMR.
From the above, it would appear that the sources and trans-
mission routes of AMR in wildlife are still not clear, meaning that
we do not know how the various parts of the puzzle fit together.Antimicrobial Resistance in Wild Boar in Europe
Wild boar (Sus scrofa) is considered one of the most extensively
distributed large mammals of the world, with its distribution rang-
ing from western Europe and the Mediterranean basin to eastern
Russia, Japan and South-east Asia. Across Europe, wild boar popu-
lations have dramatically increased their distribution and number
over the last decades (Massei et al. 2015; see also Chapters 21 and
31 this book), occupying a wide variety of environments, ranging
from natural habitats to urban areas. This increase is clearly illus-
trated by the number of harvested wild boar in Europe: in 2012,
it was near 2.2 million, while this number should now stand ataround 3 million (Massei et al. 2015). Clearly, such expansion has
triggered several (negative) impacts in the ecosystems, such as the
increase of disease transmission, traffic collisions, and damage to
forest and croplands. Managing such expansion is challenging and
will require the involvement of various disciplines.
In the context of AMR dynamics, wild boar is a perfect
model species to unveil the emergence, spread, and persistence
of AMR in the wildlife–livestock interface. They are ubiqui-
tous, have considerably large home ranges when compared with
smaller mammals, are unlikely to be treated with antibiotics, at
least in the wild setting, and overlap their habitat with livestock
and humans, serving as a link between human-influenced set-
tings and natural areas (Macdonald & Laurenson 2006). Big
game hunting and the consumption of wild boar meat in vari-
ous countries of the world increases the direct contact between
humans and wild boar and these are also emerging as source of
food-borne diseases in humans (Mentaberre et al. 2013), a sce-
nario that poses additional concerns for public health.
A major concern is the general European trend of either
stabilizing or decreasing numbers of hunters in most countries,
while wild boar populations are increasing in size and distribu-
tion (Massei et al. 2015). Considering that culling is the main
source of wild boar mortality, and that urban wild boar are now-
adays a reality in several European countries, it is utterly neces-
sary to understand the role of this species in the dynamics of
AMR. Moreover, this knowledge will help to identify potential
gaps in current priority strategies aimed at reducing the burden
of AMR in the environment.
Given their ecology, wild boar are foreseen as particularly
important as reservoirs and dispersers of antibiotic resistant bac-
teria. They are omnivorous, frequently feeding on anthropogenic
sources, both direct – artificial feeding – or indirect – human
garbage – near urban areas, farms and rural settings (Fonseca &
Correia 2008; Navarro-Gonzalez et al. 2013). This strong associ-
ation between humans (urban settings), livestock (semi-natural
settings) and wildlife (natural settings) makes them particularly
susceptible to a greater exposure to antibiotic-resistant bacteria
of human origin; as a consequence, wild boar populations are a
key epidemiological link between humans, livestock, and wild-
life (Figure 38.1).
Several studies provide evidence that wild boar can act
as true wildlife reservoirs for infectious diseases, and once
infected they can transmit pathogens to livestock and humans
(Meng et al. 2009). For example, wild boar is able to maintain
Mycobacterium bovis and can probably transmit it to livestock.
Humans can also be infected with Hepatitis E virus through
contact with infected wild boar (Meng et al. 2009). Streptococcus
suis, a formerly neglected, newly emerging MDR zoonotic
pathogen, is one of the major pathogens that leads to substantial
economic losses in the intensive swine industry and previous
reports have suggested that this microorganism is an important
reservoir and disseminator of resistance genes. However, infor-
mation on the incidence of this pathogen in wild boar is scarce
(but see Baums et al. 2007).
Even though investigations on the presence of antibiotic-
resistant bacteria in wild boar are still in their infancy in
Europe, several studies have shown the potential role of this.04013:02:28